"Let's get this straight. We're debating between a big-spending, debt-ceiling-raising fiscal liberal, a moon-colony guy, a moderate from Massachusetts, or a Texan with a real plan to balance the budget," begins an announcer, speaking with a rapid Texas twang.

Images of his opponents accompany the slams against them, including Newt Gingrich wearing a space suit.

"Ron Paul isn't playing games," the voice-over continues – against a backdrop of an Etch-A-Sketch, a reference to the recent gaffe by the Romney campaign – before labeling Congressman Paul, at the end, a "big, bold Texan."

The message is plain: Paul isn't going anywhere, and with his home state of Texas – and its 152 delegates – up for grabs on May 29, he can still have an impact on the race. That might be even more true as of Tuesday, when Rick Santorum announced that he was suspending his campaign, saying the "race is over for me."

But with Mr. Santorum's exit virtually sealing the nomination for Mitt Romney, the question arises: How successful has he been in his second go-round as a presidential candidate?

In some cases, he underperformed expectations.

He didn't win a single state, despite expectations that he might take Alaska or North Dakota. He performed better in caucus states, but not as well as some experts had predicted.

Of the three remaining candidates, he has the fewest number of delegates: 51 in the latest Associated Press count, compared with 661 for Mr. Romney.

But by the most important measure – the number of votes he received – Paul was a much bigger player this year than in 2008.

In a "living autopsy" of Paul's campaign, The New York Times's Micah Cohen compared the votes and delegates Paul won by Super Tuesday in 2008 (when 27 states had voted) with the votes he's received so far this year in the 32 states that have held contests. Paul's share of the votes was 4 percent in 2008, compared with 10 percent in 2012. He's also received nearly twice the number of total votes.

In accounting for the change, Mr. Cohen writes that, "It is possible that Mr. Paul has simply run a better campaign. But the more likely explanation is that the mood of the country is more aligned to Paul’s views than it was in 2008." Factors include the rise of the tea party and changing opinions on the wars in Iraq and Afghanistan (which Paul opposes).

None of that gets Paul any closer to the White House. But he may still have some sway in the Republican Party and the fall election – arguably more than Mr. Gingrich or even Santorum.

For one thing, Paul's followers are famously loyal – to their candidate, far more than to the Republican Party. If Paul were to launch a third-party campaign (a possibility about which many have speculated) he could effectively torpedo Romney's chances.

"Paul is in a much stronger bargaining position than Gingrich to extract promises from Romney because he can do far more damage if he isn’t placated. That’s why – though both men have zero chance of being their party’s standard-bearer – Paul matters more than Gingrich," argues theWashington Post's Chris Cillizza.

Almost certainly, Paul's campaign will keep going to the end in order to keep his platform in the GOP conversation. In fact, he just announced an "in it to win it" moneybomb, hoping to raise $2 million on April 15.

Paul's ideas – particularly on the dangers of debt – have already crept into GOP rhetoric. No one knows at this point exactly what Paul may want from Romney, but expect him to continue to be a major voice.